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PubMed2004

Comparison between two hand-held autorefractors: the Sure-Sight and the Retinomax.

PURPOSE: To compare the results of manifest refraction obtained with two different hand-held autorefractors (Sure-Sight, Welch Allyn Co. and Retinomax 1, Nikon Inc.) and with the Topcon RMA 6000 on-table autorefractor in order to estimate any potential bias between these refractometers and to compare the diagnostic performances of these two hand-held autorefractors as screening devices. METHODS: Ninety-eight children were refracted under manifest conditions with the three above-mentioned refractometers and under cycloplegic conditions with the Topcon on-table autorefractor, or by means of retinoscopy. The agreement between the manifest measurements obtained with the three different autorefractors was studied using the method of Bland and Altman. The validity of several thresholds of manifest refractive anomalies as measured with the Sure-Sight and with the Retinomax was estimated by receiver operating characteristic (ROC) curves using cycloplegic measures as reference. results There is a spherical positive bias of 1 D between the Sure-Sight and the Retinomax and better agreement between the Topcon and the Retinomax. The surface area indexes of the ROC curves and the diagnostic performances in term of sensitivity and specificity are better with the Retinomax in cases of hyperopia, astigmatism and anisometropia. For myopia, the Sure-Sight has better performance. CONCLUSIONS: The results suggest that either device may be sufficient for assessing refractive errors in children in a screening setting. However, because of a bias between both refractometers in measuring the sphere, distinctive referral criteria must be chosen for the detection of hyperopia and myopia. The diagnostic performance is slightly in favor of the Retinomax.

Adolescent↗
PubMed2005

Prevalence and outcomes of childhood visual disorders.

PURPOSE: This population-based study examines the prevalence of childhood visual disorders: amblyopia (strabismus, refractive errors) and organic disease. It also assesses treatment outcomes, visual impairment and residual amblyopia. METHODS: 1582 children were retrospectively analysed on treatment completion (age 8-9 years). Significant visual disorders included: esotropia, exotropia, anisometropia (hyperopia > or = 1.50DS, astigmatism > or = 1.00DC, myopia > or = 1.50DS), ametropia (hyperopia > or = 1.50DS, astigmatism > or = 1.0DC, myopia > or = 0.75DS) and organic defects. RESULTS: 198 children (12.5%) had a significant visual disorder: strabismus (3.98%), eso:exo rate 5:1, anisometropia (2.34%), ametropia (5.82%), organic defects (0.38%). Organic disease caused visual handicap (< 6/18 in better eye) in 0.13%. Amblyopic visual impairment (6/18; 6/24-6/60) occurred in 1.13%; 2.02% had residual amblyopia (6/12 or worse). CONCLUSIONS: Childhood visual disorders are a common problem. Unfavourable visual outcomes in esotropia are related to two sub-groups and particularly with poor concordance to treatment. Suggested strategies to improve outcomes include health promotion, an "Amblyopia Nurse" and a "Patch Club".

Amblyopia↗
PubMed1975

Variations in refractive change induced by Cyclogyl upon children with differing degrees of ametropia.

The effect of cycloplegic drugs on refraction is complicated by the presence of many variables. This study is concerned with one of these: the type and degree of refractive error. A manifest and a cycloplegic refraction were performed on 170 eyes. The difference was determined in each case and tabulated according to the type of ametropia. This experiment showed that in every instance the cycloplegic estimate was equal to or greater in hyperopia or less in myopia than when performed without drugs. The greatest difference occurred in hyperopia, decreasing to zero once myopia was reached.

Accommodation, Ocular↗
PubMed1986

Clinical comparison of the visual parameters in infants with intrauterine growth retardation vs. infants with normal birth weight.

We measured vision function in a number of 7-month-old infants with intrauterine growth retardation (IUGR) and compared these findings to those for 7-month-old infants of normal birth weight. The IUGR infants had an average visual acuity of 6/162 (20/540) and an average spherical refractive error of 1.49 D hyperopia. The normal birth weight infants had an average visual acuity of 6/118.8 (20/396) and an average spherical refractive error of 0.94 D hyperopia. However, the differences between the infant groups for visual acuity and refractive error were not statistically significant. Anisometropia, astigmatism, and strabismus were infrequent for both infant groups. The results of this study suggest that IUGR infants have visual abilities resembling those of normal birth weight infants.

Astigmatism↗
PubMed1997

Hard contact lenses alter accommodative gain but do not prevent refractive adaptation in chicks.

This study compared the compensatory response to hyperopic defocus imposed on chicks in two different ways: (1) with-10 D spectacle lenses, and (2) with plano hard contact lens. The hyperopia seen with the contact lenses in situ was a consequence of their flat profile relative to the chick cornea, resulting in a negative fluid lens of approximately 16 D at day 2 and 9 D by day 10. This decrease with age reflects the corneal flattening that accompanies normal eye growth. By optically neutralizing the cornea, the contact lenses also had two other important effects: (1) a reduction in refractive astigmatism to almost negligible levels, and (2) a reduction in accommodative gain. The latter effect reflects the loss of the corneal component of the chick's accommodation and was estimated to be of the order of 40 to 57%, based on measurements made using topically applied nicotine to stimulate accommodation. Thus any estimate of the imposed hyperopic defocus based on accommodative effort required to overcome such errors will be too large. Chicks wearing either lens type on a continuous basis from hatching to 10 days only partially compensated for the imposed hyperopia through an increase in vitreous chamber growth. However, the effects were smaller in the spectacle lens group (e.g., a mean myopic shift of -4.1 +/- 2.3 D compared to -6.3 +/- 2.4 D for the contact lens group at day 10), although both groups experienced similar amounts of hyperopic defocus around day 10 (effective power of -10 D spectacle lens: -9.4 D). The changes seen in the spectacle lens group thus represent poorer compensation, i.e., 44 vs. 71% of the imposed error. However, overcompensation is the predicted effect, if any, of the accommodative deficit imposed on the contact lens group, and this was not seen. That compensation, albeit incomplete, occurred with the contact lens as well as the spectacle lens, suggests that neither accommodation nor astigmatism are fundamental cues for emmetropization as modeled here.

Accommodation, Ocular↗
PubMed2000

Laboratory, clinical, and kindergarten test of a new eccentric infrared photorefractor (PowerRefractor).

PURPOSE: Photorefraction is a convenient way to determine refractive state from a distance. It is, therefore, useful for measuring infants and noncooperative subjects. However, its reliability (or precision) and accuracy (or validity) has been questioned. In a study in subjects without cycloplegia, we have tested whether, after complete automatization, eccentric photorefraction at a 1-m distance can be as reliable as a common autorefractor. METHODS: In a laboratory study of 15 student subjects without the use of cycloplegia (30 eyes, refractive errors ranging from -6 D to +6 D), age 25 to 31 years, the photorefractive measurements were compared with spectacle prescriptions. In a clinical study, photorefraction, autorefraction, and subjective refraction were performed in 40 patients without cycloplegia (refractive errors ranging from -4 D to +4 D), most of them with various ocular pathologies. Subjective refractions were obtained by an experienced clinical ophthalmologist but were not accessible to the examiner who used the two refractors. Visual acuity was 20/20 or better except for five subjects. Ages ranged from 6 to 75 years. In the kindergarten screening study, 108 children aged 3 to 6 years were screened for refractive errors. RESULTS: In the laboratory study, it was found that the mean difference between spectacle prescription and PowerRefractor measurements was < 0.6 D for spheres and below 0.4 D for cylinders. In the clinical study, data were obtained by all three procedures in 78 eyes. The photorefractor and the autorefractor performed similarly for spheres (mean absolute dioptric difference between refractor and subjective measure: 0.593 D and 0.696 D) and cylinders (mean absolute dioptric differences: 0.399 D and 0.389 D). However, the photorefractor was superior with regard to the measurement of the magnitude and axis of astigmatism (mean weighted difference between objective and subjective axis 0.644 D and 0.769 D, respectively). In the kindergarten study, it was found that the PowerRefractor was very convenient to handle. The autorefractor measured more myopic refractions than the PowerRefractor (mean of the left eyes 0.11 +/- 1.1 D vs. 0.62 +/- 0.53 D, p < 0.001). There was no indication that the PowerRefractor failed to detect hyperopia, because all but one child with more than 2 D of hyperopia measured with autorefractor (n = 7) was also hyperopic with the PowerRefractor. Furthermore, presenting an interesting fixation target at a 3-m distance did not cause more hyperopic refractions, indicating that the camera of the PowerRefractor at a 1-m distance was not a significant stimulus to accommodation. CONCLUSIONS: The PowerRefractor was shown to have comparable or slightly better reliability and accuracy than a modern autorefractor; however, it has major advantages over current autorefractors in that it is faster, measures both eyes at once, and gives interpupillary distance, pupil size, and information on the alignment of the eyes at the same time.

Adolescent↗
PubMed1993

Indications, results, and complications of refractive corneal surgery with lasers.

Large numbers of patients are being treated for myopia, hyperopia, and astigmatism using the excimer laser. For many patients who are treated for myopia and hyperopia, the procedure is elective and these treatments remain investigational. The use of other lasers for refractive surgery is at an earlier stage, with human trials commencing for infrared lasers. Animal studies are being performed for pulsed picosecond and solid-state ultraviolet lasers. The indications for refractive treatment should be clearly defined, although the results of laser application remain the subject of investigation. Complications of laser application to the cornea occur in the immediate, short-term, and long-term posttreatment period. A continual improvement in refractive results along with a reduction in complications remains the goal of laser refractive research.

Forecasting↗
PubMed2006

Bioptics: where do things stand?

PURPOSE OF REVIEW: Bioptics treats complex refractive errors by combining refractive techniques with different mechanisms of action, usually using an intraocular implant (a phakic or pseudophakic intraocular lens) followed by a corneal procedure (laser ablation, intrastromal implant). RECENT FINDINGS: In myopia and hyperopia, bioptics with phakic intraocular lenses or refractive lens exchange and subsequent excimer laser yields improved predictability and unchanged safety, compared with sole intraocular lens surgery. Complications are related mainly to intraocular lenses. In keratoconus and pellucid marginal degeneration, intracorneal rings have been successfully combined with phacoemulsification or with phakic intraocular lenses in a limited number of eyes. In the author's series, angle-supported phakic intraocular lenses were implanted in 12 eyes to correct a mean regression of -8 D after excimer laser (reverse bioptics), achieving a mean spherical equivalent of -0.3 D, mean best spectacle-corrected visual acuity of 0.7, and mean uncorrected visual acuity of 0.5, with 83% of eyes within 0.5 D of spherical equivalent. SUMMARY: Bioptics improves vision and halos and adds no particular risks to phakic or pseudophakic intraocular lens implantation in either myopia or hyperopia. Reverse bioptics, with phakic intraocular lenses or refractive lens exchange, can be used to correct regressed corneal surgery.

Cornea↗
PubMedDate not supplied

Calculation of intraocular lens power after corneal refractive surgery.

PURPOSE: Underestimation of required intraocular lens (IOL) power with resultant hyperopia is common in post-corneal refractive surgery eyes. A number of methods to minimize error have been proposed but most studies have been small and theoretical. METHODS: We retrospectively reviewed 34 eyes that had undergone routine phacoemulsification and IOL implantation after photorefractive keratectomy or laser in situ keratomileusis. Sixteen eyes were included in the final analysis. Using known pre- and postoperative data, four methods were used to obtain keratometric values combined with three common IOL formulae (Holladay 2, SRK/T and Hoffer Q) and Koch's published Double-K nomogram. The Double-K method was also used in conjunction with the Holladay 2 formula. Target refractions were calculated and then compared to actual postoperative results. RESULTS: The Clinical History method at the spectacle plane produced the lowest mean K-values. Shammas adjustment formula combined with the Holladay 2 and Hoffer Q produced results closest to emmetropia. The Double-K methods produced the least number of hyperopic results. Overall, all methods would have resulted in unacceptably high rates of hyperopia and deviation from target refraction. CONCLUSIONS: No method produces acceptably consistent results because modern IOL formulae were designed for presurgical eyes. Accuracy will only be improved when new IOL formulae based on the anatomy of postrefractive eyes become available. Shammas adjustment formula and regression formulae are viable alternatives especially when there is a lack of preoperative data. The Double-K methods are best suited to avoiding a hyperopic surprise.

Algorithms↗
PubMed1986

Mass screening of children for strabismus or ametropia with two-flash photoskiascopy.

UNLABELLED: 169 non-selected 1-5 year-old children (338 eyes) were screened by two-flash photoskiascopy with an autofocus camera for strabismus, high anisometropia and high ametropias without cycloplegia. The photography was performed by nurses or technicians and the photographs were analyzed by an optician. The sensitivity of the method for the refractive errors was tested with an optical demonstration eye. FINDINGS: 5 esotropias, 1 exotropia, 1 straight-eyed hypermetropic anisometropia of 4 diopters; 1 false positive high hyperopia (of +2.5 diopters) of both eyes. The examination of the photographs showed slight refractive errors in 33 cases (66 eyes; 19.5%): two of them of symmetrical myopia of -1.0 and -1.75 diopters and 31 of symmetrical hyperopia of +0.25 to +4.25 diopters in retinoscopy. 128 cases (256 eyes; 76%) were normal on the photographs. Of these, 37 non-selected cases (74 eyes) were checked clinically and were symmetrical cases of -1.0 to +3.25 diopters on retinoscopy. No false negative cases appeared among these control cases. 2,4% of the photographs failed technically or because of noncooperation of the children. Two-flash photoskiascopy, performed by technicians or nurses provides a valuable tool for mass screening of infants for strabismus and/or ametropia causing amblyopia.

Child, Preschool↗
PubMed1986

Screening of infants for strabismus and refractive errors with two-flash photorefraction with and without cycloplegia.

35 1/2-year-old and 31 1-year-old children were screened by two-flash photorefraction for strabismus and refractive errors with and without cycloplegia. The sensitivity of the method to detect refractive errors was tested with an optical demonstration eye. All the children were examined clinically to compare the sensitivity of the method. Every child co-operated with the photography, but 4 children did not co-operate in the clinical examination and were thus excluded from the refractive material, as were also two cases of esotropias which were found. There were no false positive or negative strabismus cases. The total refractive material consisted of 120 eyes. The method was clearly more sensitive for refractive errors with cycloplegia. Even one hyperopia of +5.25 D(OD) and +6.0 D(OS) was underestimated without cycloplegia. In the material there were no cases of anisometropia of over 1.0 D in spherical equivivalent that would cause a potential risk for amblyopia. A rather good correlation of refractive results existed with the method in cycloplegia. With partial overlapping of emmetropic and moderate hyperopic cases. The screening of children aged 1/2-1 year with two-flash photorefraction is simple to perform. The underestimation of symmetrical hyperopias should be accepted when cycloplegia is not used. Only one successful photograph of each child is necessary for the interpretation.

Accommodation, Ocular↗
PubMed1989

Occurrence of eye disorders and need for treatment in the elderly in special dwellings and nursing homes [corrected].

The prevalence of eye disorders and need for ophthalmological procedures due to pathological processes were studied among elderly people living in 8 special dwellings [corrected] and nursing homes in northern Finland (N = 268). The participation rate was 100%. Hyperopia was the most common disorder found (men: 78%, women 77-78%). Macular degeneration was found in 54-55% of men and 45-46% of women, senile cataract in 32-33% of men and 28-31% of women and palpebral dermatochalasis or blepharochalasis in 25-26% of men and 31% of women. Hyperopia was more common in younger persons, but senile cataract, macular degeneration and palpebral dermatochalasis or blepharochalasis were more common in older persons. Basic ophthalmological examinations led to a high number of secondary procedures. Ophthalmological treatment and rehabilitation seemed to be neglected in these Finnish special dwellings [corrected] and nursing homes. Because sight is an important determinant of elderly people's ability to manage their daily activities, the authors propose that more attention should be paid to the screening of ophthalmological problems and to ophthalmological treatment and rehabilitation in special dwellings and nursing homes [corrected].

Age Factors↗
PubMed2007

Refractive errors in neurofibromatosis type 1 and type 2.

OBJECTIVE: To document the prevalence of refractive errors in patients with neurofibromatosis type 1 (NF1) and type 2 (NF2) and to compare it with that of age- and sex-matched controls. METHODS: 82 patients with NF1, 21 patients with NF2 and 103 age- and sex-matched controls were evaluated in this prospective observational case-control study. Cycloplegic autorefraction and dilated fundus examination were performed. Myopia was defined as the spherical equivalent refraction of at least -0.50 diopters (D), hyperopia as the spherical equivalent refraction of at least 2.0 D and astigmatism as the cylinder of at least 1.0 D. Main outcome measures were refractive error, IQ, years of education, height, weight and body mass index (BMI). RESULTS: The prevalence of myopia was 23.1% in patients with NF1, 23.8% in patients with NF2 and 16.5% in age- and sex-matched controls. These differences were significant (p<0.03, p<0.03), and adjusting for intelligence, education, height, weight and BMI increased the significance of this finding (p<0.001, p<0.001). The prevalences of astigmatism and hyperopia were similar in both groups. CONCLUSION: A high prevalence of myopia seems to be an additional feature of NF1 and NF2.

Case-Control Studies↗
PubMed2005

Lenticular accommodation in relation to ametropia: the chick model.

Our goal was to determine whether experimentally induced ametropias have an effect on lenticular accommodation and spherical aberration. Form-deprivation myopia and hyperopia were induced in one eye of hatchling chicks by application of a translucent goggle and +15 D lens, respectively. After 7 days, eyes were enucleated and lenses were optically scanned prior to accommodation, during accommodation, and after accommodation. Accommodation was induced by electrical stimulation of the ciliary nerve. Lenticular focal lengths for form-deprived eyes were significantly shorter than for their controls and accommodation-associated changes in focal length were significantly smaller in myopic eyes compared to their controls. For eyes imposed with +15 D blur, focal lengths were longer than those for their controls and accommodative changes were greater. Spherical aberration of the lens increased with accommodation in both form-deprived and lens-treated birds, but induction of ametropia had no effect on lenticular spherical aberration in general. Nonmonotonicity from lenticular spherical aberration increased during accommodation but effects of refractive error were equivocal. The crystalline lens contributes to refractive error changes of the eye both in the case of myopia and hyperopia. These changes are likely attributable to global changes in the size and shape of the eye.

Accommodation, Ocular↗
PubMed2003

Refractive error and visual impairment in African children in South Africa.

PURPOSE: To assess the prevalence of refractive error and visual impairment in school-aged African children in South Africa. METHODS: Random selection of geographically defined clusters was used to identify a sample of children 5 to 15 years of age in the Durban area. From January to August 2002, children in 35 clusters were enumerated through a door-to-door survey and examined in temporary facilities. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy and autorefraction under cycloplegia, and examination of the anterior segment, media, and fundus. In nine clusters, children with reduced vision and a sample of those with normal vision underwent independent replicate examinations for quality assurance. RESULTS: A total of 5599 children living in 2712 households were enumerated, and 4890 (87.3%) were examined. The prevalence of uncorrected, presenting, and best-corrected visual acuity of 20/40 or worse in the better eye was 1.4%, 1.2%, and 0.32%, respectively. Refractive error was the cause in 63.6% of the 191 eyes with reduced vision, amblyopia in 7.3%, retinal disorders in 9.9%, corneal opacity in 3.7%, other causes in 3.1%, and unexplained causes in the remaining 12.0%. Exterior and anterior segment abnormalities were observed in 528 (10.8%) children, mainly corneal and conjunctival. Myopia (at least -0.50 D) in one or both eyes was present in 2.9% of children when measured with retinoscopy and in 4.0% measured with autorefraction. Beginning with an upward trend at age 14, myopia prevalence with autorefraction reached 9.6% at age 15. Myopia was also associated with increased parental education. Hyperopia (+2.00 D or more) in at least one eye was present in 1.8% of children when measured with retinoscopy and in 2.6% measured with autorefraction, with no significant predictors of hyperopia risk. CONCLUSIONS: The prevalence of reduced vision is low in school-age African children, most of it because of uncorrected refractive error. The high prevalence of corneal and other anterior segment abnormalities is a reflection of the inadequacy of primary eye care services in this area.

Adolescent↗
PubMed2004

Ocular biometry and refraction in Mongolian adults.

OBJECTIVE: To describe the variation in ocular biometry and its association with refraction in adult Mongolians. METHODS: The study included 1800 subjects, aged 40 years or more, who were selected in two Mongolian provinces-Hövsgöl and Omnögobi-to participate in this population survey. Axial length (AL) and its components, as well as noncycloplegic autorefraction and corneal power (CP), were measured. RESULTS: Of those selected, 1617 subjects (90.0%) were examined. Mean +/- SD of AL was 23.13 +/- 1.15 mm. There was a very small but significant increase in mean AL with age (0.05 mm per decade, P = 0.03). Autorefraction was performed on 620 of 675 subjects of those examined in Omnögobi. The age and gender standardized prevalences of myopia (< -0.5 D), emmetropia, hyperopia (> +0.5 D), astigmatism (< -0.5 D of cylinder) and anisometropia (>1.0 D difference between eyes) were 17.2%, 49.9%, 32.9%, 40.9%, and 10.7%, respectively. Prevalence of myopia showed no clear trend with increasing age, whereas hyperopia, astigmatism, and anisometropia all increased monotonically. Multiple regression models revealed that AL (P < 0.001) and VCD (P < 0.001) were the strongest determinants of refractive error. CONCLUSIONS: In this cross-sectional study of adult Mongolians, a much lower prevalence of myopia was found than in other East Asian populations studied to date. The mean AL differed little between age groups, in marked contrast to data on Chinese people.

Adult↗
PubMed2004

Refractive error and visual impairment in urban children in southern china.

PURPOSE: To assess the prevalence of refractive error and visual impairment in school-age children in a metropolitan area of southern China. METHODS: Random selection of geographically defined clusters was used to identify children 5 to 15 years of age in Guangzhou. Children in 22 clusters were enumerated through a door-to-door survey and examined in 71 schools and 19 community facilities from October 2002 to January 2003. The examination included visual acuity measurements, ocular motility evaluation, retinoscopy, and autorefraction under cycloplegia and examination of the external eye, anterior segment, media, and fundus. RESULTS: A total of 5053 children living in 4814 households were enumerated, and 4364 (86.4%) were examined. The prevalence of uncorrected, presenting, and best-corrected visual acuity 20/40 or worse in the better eye was 22.3%, 10.3%, and 0.62%, respectively. Refractive error was the cause in 94.9% of the 2335 eyes with reduced vision, amblyopia in 1.9%, other causes in 0.4%, and unexplained causes in the remaining 2.8%. External and anterior segment abnormalities were seen in 1496 (34.3%) children, mainly minor conjunctival abnormalities. Media and fundus abnormalities were observed in 32 (0.73%) children. Myopia (spherical equivalent of at least -0.50 D in either eye) measured with retinoscopy affected 73.1% of children 15 years of age, 78.4% with autorefraction. The prevalence of myopia was 3.3% in 5-year-olds with retinoscopy and 5.7% with autorefraction. Females had a significantly higher risk of myopia. Hyperopia (+2.00 D or more) measured with retinoscopy was present in 16.7% of 5-year-olds, 17.0% with autorefraction. The prevalence of hyperopia was below 1% in 15-year-olds, with both methods. Astigmatism (cylinder of > or = 0.75 D) was present in 33.6% of children with retinoscopy and in 42.7% with autorefraction. CONCLUSIONS: The prevalence of reduced vision because of myopia is high in school-age children living in metropolitan Guangzhou, representing an important public health problem. One third of these children do not have the necessary corrective spectacles. Effective strategies are needed to eliminate this easily treated cause of significant visual impairment.

Adolescent↗
PubMed1989

Down syndrome. Clinical review of ocular features.

A total of 187 medical records of Down syndrome individuals over a 10-year period were reviewed retrospectively for strabismus, myopia, hyperopia, astigmatism, nystagmus, cataract, glaucoma, and other significant eye findings. This study showed that a higher proportion of these individuals than reported in previous studies had strabismus (57%). Refractive errors of myopia (22.5%), hyperopia (20.9%) and astigmatism (22%) were common. The primary care physician needs to be aware of the specific eye problems of Down syndrome individuals so that he or she may initiate or refer the patient for appropriate ophthalmologic care, because most of the eye findings in Down syndrome are treatable. Significant visual loss, a usually avoidable event in Down syndrome, should occur rarely.

Adolescent↗